Subject: [Sigtran] AS, RK , RC concepts in SE model

From: Ilie Glib <[email-masked]>
Date: Tue, 6 Dec 2005 11:40:47 +0100

Hello Folks,

According to the current definition of AS and RK there is 1:1
relationship between them. The AS is an Application Server that
process traffic routed according to the routing key, that is it
process traffic that comes from unidirectional signalling relations,
it does not process traffic that goes in the opposite direction, it
generates traffic in the opposite direction.

For example
The RK1=(OPC=2-200, DPC=2-100) is different from RK2=(OPC=2-100,
DPC=2-200). Each RK defines its own AS, in this case AS1, which
corresponds to RK1, sits in 2-200 signalling point and AS2, which
corresponds to RK2, is in 2-100, and each AS has its own RK.

Could you please clarify

Q1: What is correct 1) or 2)
1) In the described above configuration it is one AS = AS1=AS2, or otherwise
2) AS1 and AS2 are different ASes

I assume 2) is correct. Then Routing Context RC1 corresponding to RK1
is assigned in AS2 and Routing Context RC2 corresponding to RK2 is
assigned in AS1. RC1 and RC2 are different but may be the same by
chance.

Routing Context parameter is mandatory in SUA traffic messages.

In case of SE model could you please clarify

Q2: What Routing Context values will be used in traffic messages
between AS1 and AS2?
Q3: Does it depend on the direction of the message?

Q4: When RC1 is used and when RC2?

Q5: what RC shall be used by response messages?

Thank you in advance

Ilie

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 6 Dec 2005 03:53:00 -0700

Ilie,

For SE AS1==AS2 (and RK1==RK2).

For DE AS1!=AS2 (and RK1!=RK2).

You need double the AS, RC and RKs in DE as you do in SE.

Because they can't relay, IPSPs only need 1 AS betwixt them.

--brian

Ilie Glib wrote:                              (Tue, 06 Dec 2005 11:40:47)

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

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From: Ilie Glib <[email-masked]>
Date: Tue, 6 Dec 2005 12:09:30 +0100

Hello Brian,

in my view this is a considerable change of AS concept. In SIGTRAN an
AS is an application server sitting behind its ASPs/IPSPs. Now you say
an AS is a bidirectional signalling relation and not an Application
Server.

The same goes for RK,  RK1 cannot be the same as RK2, because Routing
Key defines where messages go, it defines routing.

In my view the concept of Application Server cannot be dependent on
the exchange model used. How can we make the main SIGTRAN concept
dependent on the communication model?

Any other opinions?

Regards

Ilie

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From: Ilie Glib <[email-masked]>
Date: Tue, 6 Dec 2005 12:48:59 +0100

Brian,

according to SUA RFC, IPSPs can also have relay capability. Is SUA RFC
so outdated, that it does not worth discussing it?

Thank you in advance

Ilie

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 6 Dec 2005 04:53:41 -0700

Ilie,

If that's the way you want it, I suggest you stick to the DE model.

--brian

Ilie Glib wrote:                            (Tue, 06 Dec 2005 12:09:30)

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 6 Dec 2005 04:55:23 -0700

Ilie,

SCCP relay is a different thing than MTP relay (transfer function).
MTP requires network management across the relay, SCCP doesn't.

--brian

Ilie Glib wrote:                          (Tue, 06 Dec 2005 12:48:59)

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

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From: Ilie Glib <[email-masked]>
Date: Tue, 6 Dec 2005 13:14:36 +0100

Brian,

I think SUA relay deserves as much (as little) network management as
M3UA relay does, because they use the same SCTP service (IP network).
Redundand relay nodes (IPSP) will provide the same connectivity to
IPSPs sitting behind them.

In addition, SUA RFC allows DUNA, DAVA, DUPU, to be sent from IPSP relay nodes.

Ilie

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 6 Dec 2005 06:06:41 -0700

Ilie,

I disagree.

Nevertheless, SE is 1 AS with a symmetric RK.

--brian

Ilie Glib wrote:                                                      (Tue, 06 Dec 2005 13:14:36)

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

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From: "Tolga Asveren" <[email-masked]>
Date: Tue, 6 Dec 2005 07:59:05 -0500

I also agree with Brian.

   Thanks,
   Tolga

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On
> Behalf Of Brian F. G. Bidulock
> Sent: Tuesday, December 06, 2005 8:07 AM
> To: Ilie Glib
> Cc: [email-masked]
> Subject: Re: [Sigtran] AS, RK , RC concepts in SE model
> 
> 
> Ilie,
> 
> I disagree.
>

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From: "Tolga Asveren" <[email-masked]>
Date: Tue, 6 Dec 2005 09:07:17 -0500

Ilie,

> Behalf Of Ilie Glib
> Sent: Tuesday, December 06, 2005 6:10 AM
> To: [email-masked]; Ilie Glib; [email-masked]
[TOLGA]Two points related with this:
- From M3UA stack point of view, an AS is a signaling realtionship for
SGP/ASP/IPSP cases. It is true that AS is not only a M3UA stack but the
functional areas of M3UA specification deal only with M3UA stack behavior.
If you look from architectural perspective, I would say that an AS consists
of multiple ASPs -with M3UA stack, SS7 User Parts and Application logic-,
rather than AS sits behind ASPs/IPSPs.

- From modeling point of view, 1:1 relationship between AS and RK still
holds for SE-IPSP. One can think that two ends of an SE-IPSP relationship
are different AS using the same RK. On each IPSP you still have the 1:1
relationship between AS and RK, because you care only about your local AS
definiton -it defines traffic at both ends-.
> Key defines where messages go, it defines routing.
[TOLGA]For SE-IPSP RK defines traffic at both ends. Still you have your
"local" RK to guide you for routing decisions. Obviously two sides need to
use the same RC so that messages are exchanged properly.
> dependent on the communication model?
[TOLGA]It isn't.

---

From: Ilie Glib <[email-masked]>
Date: Tue, 6 Dec 2005 15:49:36 +0100

Hello Tolga, Brian,

Thank you very much indeed for your clarifications. It  is hard for me
to understand how on earth a concept of a sink (AS) has evolved to a
concept of two sinks. Anyway,
- is this view largely accepted by the SIGTRAN community?
- Will other adaptation layers (say SUA) follow this model?

I would expect a separate draft/RFC that describes this model, one
draft per xxUA. As far as I understood a new WI is planned for M3UA
(for SG to SG), will it cover this model? How about other xxUAs?

Thank you in advance

Ilie

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From: "Tolga Asveren" <[email-masked]>
Date: Tue, 6 Dec 2005 09:55:49 -0500

Ilie,

> From: Ilie Glib [mailto:[email-masked]]
> Sent: Tuesday, December 06, 2005 9:50 AM
> To: Tolga Asveren
> Cc: [email-masked]
[TOLGA]AS never has been a "sink", even not for ASP. An AS can both send
*and* receive messages. Like I said below, this concept has not changed at
all between ASP and SE-IPSP. Please note that on each SE-IPSP the 1:1
relationship between AS and RK still hold and it is still two different AS
communicating with SE-IPSP model. What has changed is only that RK defines
trafic range at both ends -which was also possible for an ASP with
RK=DPC+OPC-, to allow a peer-to-peer model.
> - is this view largely accepted by the SIGTRAN community?
[TOLGA]This is what has been described by RFC and the bis document, just not
very clearly.

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 6 Dec 2005 08:54:26 -0700

Ilie,

An AS is a User (MTP-User, SCCP-User).  In a peer-to-peer signalling
relation without relay or transfer, there are two Users, however,
there is only one signalling relation.  Each end has an address.
the pair of addresses defines the signalling relation.  A signalling
relation is an RK, and an RC.

As Tolga puts it well, at one IPSP, there is a 1:1:1 relationship
between an AS (local concept) and RC and an RK.  Same at the other.
The RCs are the same and the RK's are symmetric (both define the
signalling relation from the view at only one end).  If you know
one RK you know the other.  Each end defines an AS (without relay)
and both form one signalling relation.

--brian

Ilie Glib wrote:                                                      (Tue, 06 Dec 2005 15:49:36)

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

---

From: Ilie Glib <[email-masked]>
Date: Tue, 6 Dec 2005 17:06:40 +0100

Tolga,

no doubts that RK had OPC and DPC as part of it at early SIGTRAN
times, and AS was both a sink and a source of traffic.
I have questioned whether it is the same AS served by both peer IPSPs
in IPSP to IPSP scenario where SE is in use. My claim was that it is
two ASes, but Brian opinion (see below) is that it is ONE AS.

May be the compromise statement would be that it is two ASes, but in
single exchange model it shall be guaranteed by provisioning that the
same RC is used for both RKs and ASes. This is in line with your,
Tolga, description given in the last two mails. RC still identifies
the RK within its IPSP.

See below for a short in line comment.

Thank you

Ilie

On 12/6/05, Tolga Asveren <[email-masked]> wrote:
> > > are different AS using the same RK.
perhaps you meant same RC and not RK.
> > > On each IPSP you still have the 1:1

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From: Ilie Glib <[email-masked]>
Date: Tue, 6 Dec 2005 17:11:31 +0100

Brian,

perfect, I was exactly after this statement.

Now, we have consensus.

Thank you very much indeed.

Ilie